Represents a whole or partial calendar date, such as a birthday. The time of day and time zone are either specified elsewhere or are insignificant. The date is relative to the Gregorian Calendar. This can represent one of the following:
- A full date, with non-zero year, month, and day values.
- A month and day, with a zero year (for example, an anniversary).
- A year on its own, with a zero month and a zero day.
- A year and month, with a zero day (for example, a credit card expiration date).
Year of the date. Must be from 1 to 9999, or 0 to specify a date without a year.
Month of a year. Must be from 1 to 12, or 0 to specify a year without a month and day.
Day of a month. Must be from 1 to 31 and valid for the year and month, or 0 to specify a year by itself or a year and month where the day isn't significant.